1. Field of the Invention
The present invention relates to an electron-emitting apparatus using electron-emitting devices. More particularly, the present invention relates to the structure of an acceleration electrode for accelerating emitted electrons.
2. Related Background Art
Display panels as thin type image display apparatus have been used conventionally for the applications to televisions, computer terminals, advertisement media, sign boards and the like. Such thin type image display apparatus include an image display apparatus using electron-emitting devices, an image display apparatus utilizing plasma discharge, an image display apparatus using liquid crystal, an image display apparatus using a vacuum fluorescent display tube and the like.
A wall mount television having a screen size of 40 inches or larger has recently drawn attention, which positively utilizes the features of a thin type image display panel. Among such image display panels, a display apparatus using electron-emitting devices has drawn attention because of its commercial excellence in good image quality and low power consumption.
The operation principle of a display apparatus using electron-emitting devices is similar to a conventional cathode ray tube (CRT), i.e., electrons are emitted in a vacuum container and electrons are collided with phosphor applied with a high voltage to cause a luminescence phenomenon.
This high voltage is about 15 kV to 25 kV for CRT, and about 10 kV to 15 kV for a display apparatus using electron-emitting devices. For this reason, techniques have been proposed which use an electrical earth connection structure and an electrical insulating structure near the phosphor applied with a high voltage.
A conventional electrical earth connection structure for CRT will be described with reference to FIG. 17. FIG. 17 is a transverse sectional view of a general CRT as a conventional image display apparatus.
Referring to FIG. 17, reference numeral 1700 represents a face plate whose inner side is provided with phosphor for displaying an image and a conductive film. Reference numeral 1701 represents a funnel constituting a vacuum container of CRT, and reference numeral 1702 represents a metal tension band for explosion proof. Reference numeral 1703 represents a mount lug formed on the outer periphery of the tension band 1702. CRT is mounted in the housing of the image display apparatus such as a television by using the mount lug 1703.
Reference numeral 1704 represents a low resistance film containing carbon or the like and formed on the outer wall of the funnel. The low resistance film is coated on the whole outer wall of the funnel excepting an area near a high voltage applying unit 1707 to be described later. Reference numeral 1705 represents a ground (GND) cable for connecting the metal tension band (explosion proof band) 1702 and low resistance film 1704 to the earth potential of the housing. Reference numeral 1706 represents an earth. Specifically, the end of the GND cable is connected via a terminal to an earth potential pattern of an electric circuit in the CRT housing (not shown).
Reference numeral 1707 represents a high voltage applying unit for applying a high voltage to the conductive film of the face plate. The high voltage applying unit has an electrical connection structure in an insulating cap. Reference numeral 1708 represents a high voltage cable whose one end is connected to the high voltage applying unit and whose other end is connected to a high voltage source (not shown).
Reference numeral 1709 represents an electron gun unit having a function of generating thermoelectrons in accordance with a video signal and accelerating them.
As above, a large earth potential area is formed on the funnel between the electron gun unit and face plate of CRT and on the tension band near the face plate. This earth potential area is used as a GND cable and connected to the earth potential of an electric circuit.
A high voltage is applied to the conductive film to form an image on the face plate, via the area of the funnel from which a partial area of the earth potential area is removed.
In an electrical earth connection structure of a conventional CRT, the earth connection is realized by using the electrically stable GND cable which is connected to the funnel excepting the high voltage applying unit and the area near the face plate.
There are other related arts described in the following.
JP-A-4-163833 discloses a flat panel electron beam image forming apparatus having a linear hot-cathode and a complicated electrode structure mounted in a vacuum panel. As the method of forming such a vacuum panel, a method of hermetically bonding a rear plate and a face plate with adhesive by using a frame or not by using a frame if the space between the rear and face plates is narrow. The rear plate is made of glass and formed with an electron source with a plurality of electron-emitting devices disposed in a matrix and a plurality of driving connection lines disposed in a matrix, and the face plate is made of glass and formed with an image-forming member. As the adhesive, glass material having a low melting point is used. A process of raising temperature to about 400° C. high is used for softening the glass material. During this process, various components are exposed in a high temperature environment, including the face and rear plates, an atmospheric pressure supporting spacer necessary for the vacuum panel, an anode terminal to be described later and the like. After the panel is structured, the inside of the panel is evacuated by an evacuation process to form a vacuum panel. After a process of electrically connecting an external drive circuit connection leads formed on the rear panel side, the vacuum panel is assembled in the housing to complete an image-forming apparatus.
In the image-forming apparatus using electron beams constructed as above, while an electron acceleration voltage of about several hundreds V to several tens KV is applied between two glass plates (rear plate formed with an electron source and a face plate formed with an image-forming member), an image signal is applied from an external signal processing circuit to rear plate connection leads to emit electrons at a desired position. The emitted electrons accelerated by a potential difference between two glass plates make the image-forming member on the face plate emit light to form an image. This acceleration voltage is preferably set as high as possible, at least about several kV in order to obtain luminescence of good color when a normal phosphor is used as the image-forming member. In order to apply a voltage of about several kV to the image-forming member, the connection structure of a voltage supply terminal is desired to take discharge and high voltage into consideration.
Such an image-forming apparatus has a structure equipped with an anode connection unit for supplying a high voltage to the image-forming member. For example, in the anode terminal structure described in JP-A-10-326581, a high voltage supplied from a high voltage source of the image-forming apparatus is supplied via a high voltage cable to the anode connection unit of the rear plate, and via a lead wire and via a lead wire of the image-forming member on the face plate, to the image-forming member.
Another related art is JP-A-2000-260359 which discloses the structure of applying a high voltage through an electron source substrate formed with electron-emitting devices.
Another related art is JP-A-5-273592 which discloses the structure in which an earth terminal of a control substrate of a liquid crystal panel is made in contact with a clip which is in turn made in contact with a frame member to be connected to the ground.
JP-A-9-160505 discloses the structure of a CRT earth member.